Remote control of mechanochemical reactions under physiological conditions using biocompatible focused ultrasound.

External control of chemical reactions in biological settings with spatial and temporal precision is a grand challenge for noninvasive diagnostic and therapeutic applications. While light is a conventional stimulus for remote chemical activation, its penetration is severely attenuated in tissues, which limits biological applicability. On the other hand, ultrasound is a biocompatible remote energy source that is highly penetrant and offers a wide range of functional tunability. Coupling ultrasound to the activation of specific chemical reactions under physiological conditions, however, remains a challenge. Here, we describe a synergistic platform that couples the selective mechanochemical activation of mechanophore-functionalized polymers with biocompatible focused ultrasound (FUS) by leveraging pressure-sensitive gas vesicles (GVs) as acousto-mechanical transducers. The power of this approach is illustrated through the mechanically triggered release of covalently bound fluorogenic and therapeutic cargo molecules from polymers containing a masked 2-furylcarbinol mechanophore. Molecular release occurs selectively in the presence of GVs upon exposure to FUS under physiological conditions. These results showcase the viability of this system for enabling remote control of specific mechanochemical reactions with spatiotemporal precision in biologically relevant settings and demonstrate the translational potential of polymer mechanochemistry.

Nociception and hypersensitivity involve distinct neurons and molecular transducers in Drosophila.

Acute nociception is essential for survival by warning organisms against potential dangers, whereas tissue injury results in a nociceptive hypersensitivity state that is closely associated with debilitating disease conditions, such as chronic pain. Transient receptor potential (Trp) ion channels expressed in nociceptors detect noxious thermal and chemical stimuli to initiate acute nociception. The existing hypersensitivity model suggests that under tissue injury and inflammation, the same Trp channels in nociceptors are sensitized through transcriptional and posttranslational modulation, leading to nociceptive hypersensitivity. Unexpectedly and different from this model, we find that in Drosophila larvae, acute heat nociception and tissue injury-induced hypersensitivity involve distinct cellular and molecular mechanisms. Specifically, TrpA1-D in peripheral sensory neurons mediates acute heat nociception, whereas TrpA1-C in a cluster of larval brain neurons transduces the heat stimulus under the allodynia state. As a result, interfering with synaptic transmission of these brain neurons or genetic targeting of TrpA1-C blocks heat allodynia but not acute heat nociception. TrpA1-C and TrpA1-D are two splicing variants of TrpA1 channels and are coexpressed in these brain neurons. We further show that Gq-phospholipase C signaling, downstream of the proalgesic neuropeptide Tachykinin, differentially modulates these two TrpA1 isoforms in the brain neurons by selectively sensitizing heat responses of TrpA1-C but not TrpA1-D. Together, our studies provide evidence that nociception and noncaptive sensitization could be mediated by distinct sensory neurons and molecular sensors.

Any-nucleus distributed active programmable transmit coil.

PURPOSE: There are 118 known elements. Nearly all of them have NMR active isotopes and at least 39 different nuclei have biological relevance. Despite this, most of today's MRI is based on only one nucleus-1H. To facilitate imaging all potential nuclei, we present a single transmit coil able to excite arbitrary nuclei in human-scale MRI. THEORY AND METHODS: We present a completely new type of RF coil, the Any-nucleus Distributed Active Programmable Transmit Coil (ADAPT Coil), with fast switches integrated into the structure of the coil to allow it to operate at any relevant frequency. This coil eliminates the need for the expensive traditional RF amplifier by directly converting direct current (DC) power into RF magnetic fields with frequencies chosen by digital control signals sent to the switches. Semiconductor switch imperfections are overcome by segmenting the coil. RESULTS: Circuit simulations demonstrated the effectiveness of the ADAPT Coil approach, and a 9 cm diameter surface ADAPT Coil was implemented. Using the ADAPT Coil, 1H, 23Na, 2H, and 13C phantom images were acquired, and 1H and 23Na ex vivo images were acquired. To excite different nuclei, only digital control signals were changed, which can be programmed in real time. CONCLUSION: The ADAPT Coil presents a low-cost, scalable, and efficient method for exciting arbitrary nuclei in human-scale MRI. This coil concept provides further opportunities for scaling, programmability, lowering coil costs, lowering dead-time, streamlining multinuclear MRI workflows, and enabling the study of dozens of biologically relevant nuclei.

Miniaturized preamplifier integration in ultrasound transducer design for enhanced photoacoustic imaging.

Photoacoustic imaging (PAI) utilizes the photoacoustic effect to record both vascular and functional characteristics of a biological tissue. Photoacoustic signals have typically low amplitude that cannot be read efficiently by data acquisition systems. This necessitates the use of one or more amplifiers. These amplifiers are somewhat bulky (e.g., the ZFL-500LN+, Mini-Circuits, USA, or 351A-3-50-NI, Analog Modules Inc., USA). Here, we describe the fabrication and development process of a transducer with a built-in low-noise preamplifier that is encased within the transducer housing. This new, to the best of our knowledge, design could be advantageous for applications where a compact transducer + preamplifier is required. We demonstrate the performance of this compact detection unit in a laser scanning photoacoustic microscopy system by imaging a rat ear ex vivo and a rat brain vasculature in vivo.

Histoplasty Modification of the Tumor Microenvironment in a Murine Preclinical Model of Breast Cancer.

PURPOSE: To develop a noninvasive therapeutic approach able to alter the biophysical organization and physiology of the extracellular matrix (ECM) in breast cancer. MATERIALS AND METHODS: In a 4T1 murine model of breast cancer, histoplasty treatment with a proprietary 700-kHz multielement therapy transducer using a coaxially aligned ultrasound (US) imaging probe was used to target the center of an ex vivo tumor and deliver subablative acoustic energy. Tumor collagen morphology was qualitatively evaluated before and after histoplasty with second harmonic generation. Separately, mice bearing bilateral 4T1 tumors (n = 4; total tumors = 8) were intravenously injected with liposomal doxorubicin. The right flank tumor was histoplasty-treated, and tumors were fluorescently imaged to detect doxorubicin uptake after histoplasty treatment. Next, 4T1 tumor-bearing mice were randomized into 2 treatment groups (sham vs histoplasty, n = 3 per group). Forty-eight hours after sham/histoplasty treatment, tumors were harvested and analyzed using flow cytometry. RESULTS: Histoplasty significantly increased (P = .002) liposomal doxorubicin diffusion into 4T1 tumors compared with untreated tumors (2.12- vs 1.66-fold increase over control). Flow cytometry on histoplasty-treated tumors (n = 3) demonstrated a significant increase in tumor macrophage frequency (42% of CD45 vs 33%; P = .022) and a significant decrease in myeloid-derived suppressive cell frequency (7.1% of CD45 vs 10.3%; P = .044). Histoplasty-treated tumors demonstrated increased CD8+ (5.1% of CD45 vs 3.1%; P = .117) and CD4+ (14.1% of CD45 vs 11.8%; P = .075) T-cell frequency. CONCLUSIONS: Histoplasty is a nonablative focused US approach to noninvasively modify the tumor ECM, increase chemotherapeutic uptake, and alter the tumor immune microenvironment.

In vivo evaluation of focused ultrasound ablation surgery (FUAS)-induced coagulation using echo amplitudes of the therapeutic focused ultrasound transducer.

OBJECTIVE: Monitoring sensitivity of sonography in focused ultrasound ablation surgery (FUAS) is limited (no hyperechoes in ∼50% of successful coagulation in uterine fibroids). A more accurate and sensitive approach is required. METHOD: The echo amplitudes of the focused ultrasound (FUS) transducer in a testing mode (short pulse duration and low power) were found to correlate with the ex vivo coagulation. To further evaluate its coagulation prediction capabilities, in vivo experiments were carried out. The liver, kidney, and leg muscles of three adult goats were treated using clinical FUAS settings, and the echo amplitude of the FUS transducer and grayscale in sonography before and after FUAS were collected. On day 7, animals were sacrificed humanely, and the treated tissues were dissected to expose the lesion. Echo amplitude changes and lesion areas were analyzed statistically, as were the coagulation prediction metrics. RESULTS: The echo amplitude changes of the FUS transducer correlate well with the lesion areas in the liver (R = 0.682). Its prediction in accuracy (94.4% vs. 50%), sensitivity (92.9% vs. 35.7%), and negative prediction (80% vs. 30.8%) is better than sonography, but similar in specificity (80% vs. 100%) and positive prediction (100% vs. 100%). In addition, the correlation between tissue depth and the lesion area is not good (|R| < 0.2). Prediction performances in kidney and leg muscles are similar. CONCLUSION: The FUS echo amplitudes are sensitive to the tissue properties and their changes after FUAS. They are sensitive and reliable in evaluating and predicting FUAS outcomes.

Cranial ultrasound in preterm infants ≤ 32 weeks gestation-novel insights from the use of very high-frequency (18-5 MHz) transducers: a case series.

The quality of cranial ultrasound has improved over time, with advancing technology leading to higher resolution, faster image processing, digital display, and back-up. However, some brain lesions may remain difficult to characterize: since higher frequencies result in greater spatial resolution, the use of additional transducers may overcome some of these limitations. The very high-frequency transducers (18-5 MHz) are currently employed for small parts and lung ultrasound. Here we report the first case series comparing the very high-frequency probes (18-5 MHz) with standard micro-convex probes (8-5 MHz) for cranial ultrasound in preterm infants. In this case series, we compared cranial ultrasound images obtained with a micro-convex transducer (8-5 MHz) and those obtained with a very high-frequency (18-5 MHz) linear array transducer in 13 preterm infants ≤ 32 weeks gestation (9 with cerebral abnormalities and 4 with normal findings). Ultrasound examinations using the very high-frequency linear transducer and the standard medium-frequency micro-convex transducer were performed simultaneously. We also compared ultrasound findings with brain MRI images obtained at term corrected age. Ultrasound images obtained with the very high-frequency (18-5 MHz) transducer showed high quality and accuracy. Notably, despite their higher frequency and expected limited penetration capacity, brain size is small enough in preterm infants, so that brain structures are close to the transducer, allowing for complete evaluation.    Conclusion: We propose the routine use of very high-frequency linear probes as a complementary scanning modality for cranial ultrasound in preterm infants ≤ 32 weeks gestation. What is Known: • Brain lesions in preterm infants may remain insufficiently defined through conventional cranial ultrasound scan. • Higher frequency probes  offer better spatial resolution but have a narrower filed of exploration and limited penetration capacity. What is New: • Very high-frequency probes were compared with standard medium-frequency probes for cranial ultrasound in infants  ≤ 32 weeks' gestation. • Thanks to the smaller skull size of preterm infants, the new very high-frequency transducers allowed a complete and accurate evaluation.

The impact of high-frequency transducers on the sonographic measurements of the pyloric muscle thickness in infants.

BACKGROUND: Ultrasound is the modality of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). The evolution of high-frequency transducers in ultrasound has led to inconsistent ways of measuring the pylorus. OBJECTIVE: To standardize the measurements and evaluate the appearance of the normal and hypertrophied pylorus with high-frequency transducers. MATERIALS AND METHODS: We retrospectively analyzed abdominal ultrasounds of infants with suspected HPS from January 2019-December 2020. We classified the layers of the pylorus while assessing the stratified appearance. Two pediatric radiologists measured the muscle thickness of the pylorus independently by two methods for interrater agreement. Measurement (a) includes the muscularis propria and muscularis mucosa. Measurement (b) includes only the muscularis propria. We also evaluated the echogenicity of the muscularis propria. The interrater agreement, mean, range of the muscle thickness, and the diagnostic accuracy of the two sets of measurements were calculated. RESULTS: We included 300 infants (114 F:186 M), 59 with HPS and 241 normal cases. There was a strong agreement between the readers assessed in the first 100 cases, and ICC was 0.99 (95% CI, 0.98-0.99). Measurement (a), median thickness is 2.4 mm in normal cases and 4.8 mm in HPS. Measurement (b), median thickness is 1.4 mm in normal cases and 4.0 mm in HPS. Measurement (a) has an accuracy of 89.7% (95% CI, 85.7-92.8%) with 98.3% sensitivity and 87.6% specificity. Measurement (b) has an accuracy of 98.0% (95% CI, 95.7-99.3%) with 89.8% sensitivity and 100.0% specificity. The pylorus stratification is preserved in all normal cases and 31/59 (52.5%) cases of HPS. There was complete/partial loss of stratification in 28/59 (47.5%) cases of HPS. In all HPS cases, the muscularis propria was echogenic. CONCLUSION: Measuring the muscularis propria solely has a better diagnostic accuracy, decreasing the overlap of negative and positive cases. The loss of pyloric wall stratification and echogenic muscularis propria is only seen in HPS.

Test-retest evaluation of a notched-noise test using consumer-grade mobile audio equipment.

OBJECTIVE: The aim of this study was to investigate whether consumer-grade mobile audio equipment can be reliably used as a platform for the notched-noise test, including when the test is conducted outside the laboratory. DESIGN: Two studies were conducted: Study 1 was a notched-noise masking experiment with three different setups: in a psychoacoustic test booth with a standard laboratory PC; in a psychoacoustic test booth with a mobile device; and in a quiet office room with a mobile device. Study 2 employed the same task as Study 1, but compared circumaural headphones to insert earphones. STUDY SAMPLE: Nine and ten young, normal-hearing participants completed studies 1 and 2, respectively. RESULTS: The test-retest accuracy of the notched-noise test on the mobile implementation did not differ from that for the laboratory setup. A possible effect of the earphone design was identified in Study 1, which was corroborated by Study 2, where test-retest variability was smallest when comparing results from experiments conducted using identical acoustic transducers. CONCLUSIONS: Results and test-retest repeatability comparable to standard laboratory settings for the notched-noise test can be obtained with mobile equipment outside the laboratory.

Demonstration Study of Reflector-Based Volumetric Speed-of-Sound Imaging With Linear Ultrasound Arrays.

Conventional B-mode ultrasound imaging has difficulty in delineating homogeneous soft tissues with similar acoustic impedances, as the reflectivity depends on the acoustic impedance at the interface. As a quantitative imaging biomarker sensitive to alteration of biomechanical properties, speed-of-sound (SoS) holds promising potential for tissue and disease differentiation such as delineation of different breast tissue types with similar acoustic impedance. Compared to two-dimensional (2D) SoS images, three-dimensional (3D) volumetric SoS images achieved through a full-angle ultrasound scan can reveal more intricate morphological structures of tissues; however, they generally require a ring transducer. In this study, we introduce a 3D SoS reconstruction system that utilizes hand-held linear arrays instead. This system employs a passive reflector positioned opposite the linear arrays, serving as an echogenic reference for time-of-flight (ToF) measurements, and a high-definition camera to track the location corresponding to each group of transmit-receive data. To merge these two streams of ToF measurements and location tracking, a voxel-based reconstruction algorithm is implemented. Experimental results with gelatin phantom and ex vivo tissue have demonstrated the stability of our proposed method. Moreover, the results underscore the potential of this system as a complementary diagnostic modality, particularly in the context of diseases such as breast cancer.

Element Position Calibration for Matrix Array Transducers with Multiple Disjoint Piezoelectric Panels.

Two-dimensional ultrasound transducers enable the acquisition of fully volumetric data that have been demonstrated to provide greater diagnostic information in the clinical setting and are a critical tool for emerging ultrasound methods, such as super-resolution and functional imaging. This technology, however, is not without its limitations. Due to increased fabrication complexity, some matrix probes with disjoint piezoelectric panels may require initial calibration. In this manuscript, two methods for calibrating the element positions of the Vermon 1024-channel 8 MHz matrix transducer are detailed. This calibration is a necessary step for acquiring high resolution B-mode images while minimizing transducer-based image degradation. This calibration is also necessary for eliminating vessel-doubling artifacts in super-resolution images and increasing the overall signal-to-noise ratio (SNR) of the image. Here, we show that the shape of the point spread function (PSF) can be significantly improved and PSF-doubling artifacts can be reduced by up to 10 dB via this simple calibration procedure.

In-vitro effects of novel periodontal scalers with a planar ultrasonic piezoelectric transducer on periodontal biofilm removal, dentine surface roughness, and periodontal ligament fibroblasts adhesion.

OBJECTIVES: To compare ultrasonic scaler prototypes based on a planar piezoelectric transducer with different working frequencies featuring a titanium (Ti-20, Ti-28, and Ti-40) or stainless steel (SS-28) instrument, with a commercially available scaler (com-29) in terms of biofilm removal and reformation, dentine surface roughness and adhesion of periodontal fibroblasts. MATERIALS AND METHODS: A periodontal multi-species biofilm was formed on specimens with dentine slices. Thereafter specimens were instrumented with scalers in a periodontal pocket model or left untreated (control). The remaining biofilms were quantified and allowed to reform on instrumented dentine slices. In addition, fibroblasts were seeded for attachment evaluation after 72 h of incubation. Dentine surface roughness was analyzed before and after instrumentation. RESULTS: All tested instruments reduced the colony-forming unit (cfu) counts by about 3 to 4 log10 and the biofilm quantity (each p < 0.01 vs. control), but with no statistically significant difference between the instrumented groups. After 24-hour biofilm reformation, no differences in cfu counts were observed between any groups, but the biofilm quantity was about 50% in all instrumented groups compared to the control. The attachment of fibroblasts on instrumented dentine was significantly higher than on untreated dentine (p < 0.05), with the exception of Ti-20. The dentine surface roughness was not affected by any instrumentation. CONCLUSIONS: The planar piezoelectric scaler prototypes are able to efficiently remove biofilm without dentine surface alterations, regardless of the operating frequency or instrument material. CLINICAL RELEVANCE: Ultrasonic scalers based on a planar piezoelectric transducer might be an alternative to currently available ultrasonic scalers.

Piezoelectric Transducer-Based Structural Health Monitoring.

Piezoelectric effects were first discovered more than a hundred years ago and, since then, have been widely used across various fields [...].

Development of a Small-Footprint 50 MHz Linear Array: Fabrication and Micro-Ultrasound Imaging Demonstration.

Compact high-frequency arrays are of interest for clinical and preclinical applications in which a small-footprint or endoscopic device is needed to reach the target anatomy. However, the fabrication of compact arrays entails the connection of several dozens of small elements to the imaging system through a combination of flexible printed circuit boards at the array end and micro-coaxial cabling to the imaging system. The methods currently used, such as wire bonding, conductive adhesives, or a dry connection to a flexible circuit, considerably increase the array footprint. Here, we propose an interconnection method that uses vacuum-deposited metals, laser patterning, and electroplating to achieve a right-angle, compact, reliable connection between array elements and flexible-circuit traces. The array elements are thickened at the edges using patterned copper traces, which increases their cross-sectional area and facilitates the connection. We fabricated a 2.3 mm by 1.7 mm, 64-element linear array with elements at a 36 µm pitch connected to a 4 cm long flexible circuit, where the interconnect adds only 100 µm to each side of the array. Pulse-echo measurements yielded an average center frequency of 55 MHz and a -6 dB bandwidth of 41%. We measured an imaging resolution of 35 µm in the axial direction and 114 µm in the lateral direction and demonstrated the ex vivo imaging of porcine esophageal tissue and the in vivo imaging of avian embryonic vasculature.

Compressed Sensing for Biomedical Photoacoustic Imaging: A Review.

Photoacoustic imaging (PAI) is a rapidly developing emerging non-invasive biomedical imaging technique that combines the strong contrast from optical absorption imaging and the high resolution from acoustic imaging. Abnormal biological tissues (such as tumors and inflammation) generate different levels of thermal expansion after absorbing optical energy, producing distinct acoustic signals from normal tissues. This technique can detect small tissue lesions in biological tissues and has demonstrated significant potential for applications in tumor research, melanoma detection, and cardiovascular disease diagnosis. During the process of collecting photoacoustic signals in a PAI system, various factors can influence the signals, such as absorption, scattering, and attenuation in biological tissues. A single ultrasound transducer cannot provide sufficient information to reconstruct high-precision photoacoustic images. To obtain more accurate and clear image reconstruction results, PAI systems typically use a large number of ultrasound transducers to collect multi-channel signals from different angles and positions, thereby acquiring more information about the photoacoustic signals. Therefore, to reconstruct high-quality photoacoustic images, PAI systems require a significant number of measurement signals, which can result in substantial hardware and time costs. Compressed sensing is an algorithm that breaks through the Nyquist sampling theorem and can reconstruct the original signal with a small number of measurement signals. PAI based on compressed sensing has made breakthroughs over the past decade, enabling the reconstruction of low artifacts and high-quality images with a small number of photoacoustic measurement signals, improving time efficiency, and reducing hardware costs. This article provides a detailed introduction to PAI based on compressed sensing, such as the physical transmission model-based compressed sensing method, two-stage reconstruction-based compressed sensing method, and single-pixel camera-based compressed sensing method. Challenges and future perspectives of compressed sensing-based PAI are also discussed.

Compound Acoustic Radiation Force Impulse Imaging of Bovine Eye by Using Phase-Inverted Ultrasound Transducer.

In general, it is difficult to visualize internal ocular structure and detect a lesion such as a cataract or glaucoma using the current ultrasound brightness-mode (B-mode) imaging. This is because the internal structure of the eye is rich in moisture, resulting in a lack of contrast between tissues in the B-mode image, and the penetration depth is low due to the attenuation of the ultrasound wave. In this study, the entire internal ocular structure of a bovine eye was visualized in an ex vivo environment using the compound acoustic radiation force impulse (CARFI) imaging scheme based on the phase-inverted ultrasound transducer (PIUT). In the proposed method, the aperture of the PIUT is divided into four sections, and the PIUT is driven by the out-of-phase input signal capable of generating split-focusing at the same time. Subsequently, the compound imaging technique was employed to increase signal-to-noise ratio (SNR) and to reduce displacement error. The experimental results demonstrated that the proposed technique could provide an acoustic radiation force impulse (ARFI) image of the bovine eye with a broader depth-of-field (DOF) and about 80% increased SNR compared to the conventional ARFI image obtained using the in-phase input signal. Therefore, the proposed technique can be one of the useful techniques capable of providing the image of the entire ocular structure to diagnose various eye diseases.

Accuracy of intra-arterial line transducer levelling practice in a general intensive care unit.

BACKGROUND: The intra-arterial line is a common device intervention used in the intensive care environment to provide continuous blood pressure measurement. The transducer line is levelled to the patient's phlebostatic axis to provide accurate measurements. AIM: The aim of this study was to investigate registered nurses' accuracy at levelling the transducer to the correct anatomical position using visual judgement, compared to one done using a laser level. METHODS: Patient transducers were levelled by visual judgement and then by using a laser level. Time and mean arterial pressure (MAP) were recorded with each measurement along with any difference in transducer level between the two methods and subsequent changes in inotrope administration. RESULTS: A total of 577 MAP measurements were recorded from 178 patients; 70% of observations had a difference in transducer level, 30% of the time the inotrope rate was increased and 18% of the time the inotrope rate was reduced. The prevalence of clinically significant observations with an absolute difference of 50 mm or more in transducer placement was 25%. The mean difference in MAP measurements when a cut-off of 64 mmHg or more for laser was applied to the data was 0.22 (95% confidence interval: -0.14, 0.58, n = 513, p = 0.23), and for a cut-off of less than 64 for laser, a larger mean difference of 4.36 (95% confidence interval: 3.75, 5.28], n = 64, p < 0.001) was observed. CONCLUSIONS: Transducers were unable to be accurately levelled for haemodynamic monitoring using visual means alone. Over the range of patient MAP values examined, 25% of all observations had a clinically significant absolute difference of 50 mm or more in the transducer level position between the two methods. The visual method became increasingly inaccurate and unreliable at low MAP levels requiring medical intervention.

Transcriptome Analysis Points to BES1 as a Transducer of Strigolactone Effects on Drought Memory in Arabidopsis thaliana.

Strigolactones (SLs) are carotenoid-derived phytohormones governing a wide range of physiological processes, including drought-associated stomatal closure. We have previously shown in tomato that SLs regulate the so-called after-effect of drought, whereby stomatal conductance is not completely restored for some time during recovery after a drought spell, irrespective of the water potential. To ease the elucidation of its molecular underpinnings, we investigated whether this SL effect is conserved in Arabidopsis thaliana by contrasting the physiological performances of the wild-type with SL-depleted (more axillary growth 4, max4) and insensitive (dwarf 14, d14) mutants in a drought and recovery protocol. Physiological analyses showed that SLs are important to achieve a complete after-effect in A. thaliana, while transcriptome results suggested that the SL-dependent modulation of drought responses extends to a large subset (about 4/5) of genes displaying memory transcription patterns. Among these, we show that the activation of over 30 genes related to abscisic acid metabolism and signaling strongly depends on SL signaling. Furthermore, by using promoter-enrichment tools, we identified putative cis- and trans-acting factors that may be important in the SL-dependent and SL-independent regulation of genes during drought and recovery. Finally, in order to test the accuracy of our bioinformatic prediction, we confirmed one of the most promising transcription factor candidates mediating SL signaling effects on transcriptional drought memory-BRI-EMS SUPPRESSOR1 (BES1). Our findings reveal that SLs are master regulators of Arabidopsis transcriptional memory upon drought and that this role is partially mediated by the BES1 transcription factor.

Noncontact Manipulation of Intracellular Structure Based on Focused Surface Acoustic Waves.

Cell orientation is essential in many applications in biology, medicine, and chemistry, such as cellular injection, intracellular biopsy, and genetic screening. However, the manual cell orientation technique is a trial-and-error approach, which suffers from low efficiency and low accuracy. Although several techniques have improved these issues to a certain extent, they still face problems deforming or disrupting cell membranes, physical damage to the intracellular structure, and limited particle size. This study proposes a noncontact and noninvasive cell orientation method that rotates a cell using surface acoustic waves (SAWs). To realize the acoustic cell orientation process, we have fabricated a microdevice consisting of two pairs of focused interdigital transducers (FIDTs). Instead of rotating the entire cell, the proposed method rotates the intracellular structure, the cytoplasm, directly through the cell membrane by acoustic force. We have tested the rotational manipulation process on 30 zebrafish embryos. The system was able to orientate a cell to a target orientation with a one-time success rate of 93%. Furthermore, the postoperation survival rate was 100%. Our acoustic rotational manipulation technique is noninvasive and easy to use, which provides a starting point for cell-manipulation-essential tasks, such as single-cell analysis, organism studies, and drug discovery.

Dual-frequency resonant coil design for low-γ X-nuclear and proton magnetic resonance imaging at ultrahigh fields.

Low-γ X-nuclear MRS and imaging have played a key role in studying metabolism and physiopathology, especially at ultrahigh fields. We design and demonstrate a novel and simple dual-frequency RF resonant coil that can operate at both low-γ X-nuclear and proton frequencies. The dual-frequency resonant coil comprises an LC coil loop and a tuning-matching circuit bridged by two short wires of the desired length to generate two resonant modes: one for proton MRI and the other for low-γ X-nuclear MRS imaging with a large difference in their Larmor frequencies at ultrahigh fields. The coil parameters for the desired coil size and resonant frequencies can be determined via numerical simulations based on LC circuit theory. We designed, constructed, and evaluated several prototype surface coils and quadrature array coils for 1 H and 2 H or 17 O imaging, with small-sized (diameter ≤ 5 cm) coils evaluated using a 16.4 T animal scanner, and a large-sized (15 cm diameter) coil on a 7 T human scanner. All coils could be tuned/matched and driven in the single coil or array coil mode to the resonant frequencies of 1 H (698 and 298 MHz), 2 H (107 and 45.8 MHz), or 17 O (94.7 and 40.4 MHz) for imaging measurements and evaluation at 16.4 and 7 T, respectively. The dual-frequency resonant coil or array provides adequate detection sensitivity for 1 H MRI and excellent performance for low-γ X-nuclear MRS imaging applications, and excellent coil decoupling efficiency between the array coils at both resonant frequencies with an optimal geometric overlap. It provides a simple, cost-effective dual-frequency RF coil solution to perform low-γ X-nuclear MRS imaging for preclinical and human applications, especially at ultrahigh fields.